Propulsion engine for an aircraft

ABSTRACT

A propulsion system for an aircraft includes an electric propulsion engine. The electric propulsion engine includes an electric motor and a fan rotatable about a central axis of the electric propulsion engine by the electric motor. The electric propulsion engine also includes a bearing supporting rotation of the fan and a thermal management system. The thermal management system includes a lubrication oil circulation assembly and a heat exchanger thermally connected to the lubrication oil circulation assembly. The lubrication oil circulation assembly is configured for providing the bearing with lubrication oil. Such an electric propulsion engine may be a relatively self-sufficient engine.

FIELD OF THE INVENTION

The present subject matter relates generally to an aircraft propulsionsystem.

BACKGROUND OF THE INVENTION

A conventional commercial aircraft generally includes a fuselage, a pairof wings, and a propulsion system that provides thrust. The propulsionsystem typically includes at least two aircraft engines, such asturbofan jet engines. Each turbofan jet engine is mounted to arespective one of the wings of the aircraft, such as in a suspendedposition beneath the wing, separated from the wing and fuselage. Such aconfiguration allows for the turbofan jet engines to interact withseparate, freestream airflows that are not impacted by the wings and/orfuselage. This configuration can reduce an amount of turbulence withinthe air entering an inlet of each respective turbofan jet engine, whichhas a positive effect on a net propulsive thrust of the aircraft.

However, a drag on the aircraft including the turbofan jet engines, alsohas an effect on the net propulsive thrust of the aircraft. A totalamount of drag on the aircraft, including skin friction, form, andinduced drag, is generally proportional to a difference between afreestream velocity of air approaching the aircraft and an averagevelocity of a wake downstream from the aircraft that is produced due tothe drag on the aircraft.

Systems have been proposed to counter the effects of drag and/or toimprove an efficiency of the turbofan jet engines. For example, certainpropulsion systems incorporate boundary layer ingestion systems to routea portion of relatively slow moving air forming a boundary layer across,e.g., the fuselage and/or the wings, into the turbofan jet enginesupstream from a fan section of the turbofan jet engines. Although thisconfiguration improves propulsion efficiency by reenergizing theboundary layer airflow downstream from the aircraft, the relatively slowmoving flow of air from the boundary layer entering the turbofan jetengine generally has a nonuniform or distorted velocity profile. As aresult, such turbofan jet engines can experience an efficiency lossminimizing or negating any benefits of improved propulsion efficiency onthe aircraft.

Accordingly, a propulsion system including one or more components toimprove propulsion efficiency would be useful. More particularly, apropulsion system including one or more components to improve propulsionefficiency without causing any substantial decreases in an efficiency ofthe aircraft engines would be especially beneficial.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one exemplary embodiment of the present disclosure, a propulsionsystem is provided for an aircraft having an aft end. The propulsionsystem includes an electric propulsion engine defining a central axis.The electric propulsion engine includes an electric motor, a fanrotatable about the central axis of the electric propulsion engine bythe electric motor, and a bearing supporting rotation of the fan. Theelectric propulsion engine also includes a thermal management systemhaving a lubrication oil circulation assembly for providing the bearingwith lubrication oil, and a heat exchanger thermally connected to thelubrication oil circulation assembly.

In another exemplary embodiment of the present disclosure, a boundarylayer ingestion fan defining a central axis is provided. The boundarylayer ingestion fan includes an electric motor, a fan rotatable aboutthe central axis of the boundary layer ingestion fan by the electricmotor, and a bearing supporting rotation of the fan. The boundary layeringestion fan also includes a thermal management system having alubrication oil circulation assembly for providing the bearing withlubrication oil, and a heat exchanger thermally connected to thelubrication oil circulation assembly

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a top view of an aircraft according to various exemplaryembodiments of the present disclosure.

FIG. 2 is a port side view of the exemplary aircraft of FIG. 1

FIG. 3 is a schematic, cross-sectional view of a gas turbine enginemounted to the exemplary aircraft of FIG. 1.

FIG. 4 is a schematic, cross-sectional view of an aft engine inaccordance with an exemplary embodiment of the present disclosure.

FIG. 5 is a close up, schematic, cross-sectional view of the exemplaryaft engine of FIG. 4.

FIG. 6 is a close up, schematic, cross-sectional view of an aft enginein accordance with another exemplary embodiment of the presentdisclosure.

FIG. 7 is a close up, schematic, cross-sectional view of an aft enginein accordance with yet another exemplary embodiment of the presentdisclosure.

FIG. 8 is a schematic view of a propulsion system in accordance with anexemplary embodiment of the present disclosure including the exemplaryaft engine of FIG. 7.

FIG. 9 is a close up, schematic, cross-sectional view of an aft enginein accordance with still another exemplary embodiment of the presentdisclosure.

FIG. 10 is a close up, schematic, cross-sectional view of an aft enginein accordance with yet another exemplary embodiment of the presentdisclosure.

FIG. 11 is a close up, schematic, cross-sectional view of an aft enginein accordance with still another exemplary embodiment of the presentdisclosure.

FIG. 12 is a close up, schematic, cross-sectional view of an aft enginein accordance with yet another exemplary embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention.

As used herein, the terms “first”, “second”, and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.The terms “forward” and “aft” refer to the relative positions of acomponent based on an actual or anticipated direction of travel. Forexample, “forward” may refer to a front of an aircraft based on ananticipated direction of travel of the aircraft, and “aft” may refer toa back of the aircraft based on an anticipated direction of travel ofthe aircraft.

The present disclosure provides for an electric propulsion engine for anaircraft configured to be mounted, in certain embodiments, at an aft endof the aircraft. The electric propulsion engine includes a fan rotatableby an electric motor and features for supporting rotation of the fan.Specifically, the electric propulsion engine of the present disclosureincludes a bearing supporting, e.g., a fan shaft of the fan, and athermal management system. The thermal management system includes alubrication oil circulation assembly (for providing the bearing with alubrication oil) and a heat exchanger thermally connected to lubricationoil circulation assembly. Such a configuration may allow for the bearingto be fully lubricated and maintained within a desired operatingtemperature range during operation of the electric propulsion engine.

Referring now to the drawings, wherein identical numerals indicate thesame elements throughout the figures, FIG. 1 provides a top view of anexemplary aircraft 10 as may incorporate various embodiments of thepresent invention. FIG. 2 provides a port side view of the aircraft 10as illustrated in FIG. 1. As shown in FIGS. 1 and 2 collectively, theaircraft 10 defines a longitudinal centerline 14 that extendstherethrough, a vertical direction V, a lateral direction L, a forwardend 16, and an aft end 18. Moreover, the aircraft 10 defines a mean line15 extending between the forward end 16 and aft end 18 of the aircraft10. As used herein, the “mean line” refers to a midpoint line extendingalong a length of the aircraft 10, not taking into account theappendages of the aircraft 10 (such as the wings 20 and stabilizersdiscussed below).

Moreover, the aircraft 10 includes a fuselage 12, extendinglongitudinally from the forward end 16 of the aircraft 10 towards theaft end 18 of the aircraft 10, and a pair of wings 20. As used herein,the term “fuselage” generally includes all of the body of the aircraft10, such as an empennage of the aircraft 10. The first of such wings 20extends laterally outwardly with respect to the longitudinal centerline14 from a port side 22 of the fuselage 12 and the second of such wings20 extends laterally outwardly with respect to the longitudinalcenterline 14 from a starboard side 24 of the fuselage 12. Each of thewings 20 for the exemplary embodiment depicted includes one or moreleading edge flaps 26 and one or more trailing edge flaps 28. Theaircraft 10 further includes a vertical stabilizer 30 having a rudderflap 32 for yaw control, and a pair of horizontal stabilizers 34, eachhaving an elevator flap 36 for pitch control. The fuselage 12additionally includes an outer surface or skin 38. It should beappreciated however, that in other exemplary embodiments of the presentdisclosure, the aircraft 10 may additionally or alternatively includeany other suitable configuration of stabilizer that may or may notextend directly along the vertical direction V or horizontal/lateraldirection L.

The exemplary aircraft 10 of FIGS. 1 and 2 includes a propulsion system100, herein referred to as “system 100”. The exemplary system 100includes an aircraft engine, or rather a pair of aircraft engines, eachconfigured to be mounted to one of the pair of wings 20, and an electricpropulsion engine. More specifically, for the embodiment depicted, theaircraft engines are configured as gas turbine engines, or rather asturbofan jet engines 102, 104 attached to and suspended beneath thewings 20 in an under-wing configuration. Additionally, the electricpropulsion engine is configured to be mounted at the aft end of theaircraft 10, and hence the electric propulsion engine depicted may bereferred to as an “aft engine.” Further, the electric propulsion enginedepicted is configured to ingest and consume air forming a boundarylayer over the fuselage 12 of the aircraft 10. Accordingly, theexemplary aft engine depicted may be referred to as a boundary layeringestion (BLI) fan 106. The BLI fan 106 is mounted to the aircraft 10at a location aft of the wings 20 and/or the jet engines 102, 104.Specifically, for the embodiment depicted, the BLI fan 106 is fixedlyconnected to the fuselage 12 at the aft end 18, such that the BLI fan106 is incorporated into or blended with a tail section at the aft end18, and such that the mean line 15 extends therethrough.

Referring still to the embodiment of FIGS. 1 and 2, in certainembodiments the propulsion system further includes one or more electricgenerators 108 operable with the jet engines 102, 104. For example, oneor both of the jet engines 102, 104 may be configured to providemechanical power from a rotating shaft (such as an LP shaft or HP shaft)to the electric generators 108. Additionally, the electric generators108 may be configured to convert the mechanical power to electricalpower. For the embodiment depicted, the propulsion system 100 includesan electric generator 108 for each jet engine 102, 104. As will bediscussed below, in certain exemplary aspects, the electric generator108 for each jet engine 102, 104 may be configured as part of anaccessory gearbox for the jet engine 102, 104. Alternatively, however,in other embodiments, the electric generator 108 may be separate from anaccessory gearbox for the jet engines 102 104, and located at anysuitable position within the jet engines 102, 104 or aircraft 10.

Furthermore, the propulsion system 100 includes a power conditioner 109and an energy storage device 110. The electric generators 108 may sendelectrical power to the power conditioner 109, which may transform theelectrical energy to a proper form and either store the energy in theenergy storage device 110 or send the electrical energy to the BLI fan106. For the embodiment depicted, the electric generators 108, powerconditioner 109, energy storage device 110, and BLI fan 106 are all areconnected to an electric communication bus 111, such that the electricgenerators 108 may be in electrical communication with the BLI fan 106and/or the energy storage device 110, and such that the electricgenerators 108 may provide electrical power to one or both of the energystorage device 110 or the BLI fan 106. Accordingly, in such anembodiment, the propulsion system 100 may be referred to as agas-electric propulsion system.

It should be appreciated, however, that the aircraft 10 and propulsionsystem 100 depicted in FIGS. 1 and 2 is provided by way of example onlyand that in other exemplary embodiments of the present disclosure, anyother suitable aircraft 10 may be provided having a propulsion system100 configured in any other suitable manner. For example, it should beappreciated that in various other embodiments, the BLI fan 106 mayalternatively be positioned at any suitable location proximate the aftend 18. Further, in still other embodiments the electric propulsionengine may not be positioned at the aft end of the aircraft 10, and thusmay not be configured as an “aft engine.” For example, in otherembodiments, the electric propulsion engine may be incorporated into thefuselage of the aircraft 10, and thus configured as a “podded engine.”Alternatively, in still other embodiments, the electric propulsionengine may be incorporated into a wing of the aircraft 10, and thus maybe configured as a “blended wing engine.” Further, in other embodiments,the propulsion system 100 may not include, e.g., the power conditioner109 and/or the energy storage device 110, and instead the generator(s)108 may be directly connected to the BLI fan 106.

Referring now to FIG. 3, in at least certain embodiments, the jetengines 102, 104 may be configured as high-bypass turbofan jet engines.FIG. 3 is a schematic cross-sectional view of an exemplary high-bypassturbofan jet engine 200, herein referred to as “turbofan 200.” Invarious embodiments, the turbofan 200 may be representative of jetengines 102, 104. As shown in FIG. 3, the turbofan 200 defines an axialdirection A1 (extending parallel to a longitudinal centerline 201provided for reference) and a radial direction R1. In general, theturbofan 200 includes a fan section 202 and a core turbine engine 204disposed downstream from the fan section 202.

The exemplary core turbine engine 204 depicted generally includes asubstantially tubular outer casing 206 that defines an annular inlet208. The outer casing 206 encases, in serial flow relationship, acompressor section including a booster or low pressure (LP) compressor210 and a high pressure (HP) compressor 212; a combustion section 214; aturbine section including a high pressure (HP) turbine 216 and a lowpressure (LP) turbine 218; and a jet exhaust nozzle section 220. A highpressure (HP) shaft or spool 222 drivingly connects the HP turbine 216to the HP compressor 212. A low pressure (LP) shaft or spool 224drivingly connects the LP turbine 218 to the LP compressor 210.

For the embodiment depicted, the fan section 202 includes a variablepitch fan 226 having a plurality of fan blades 228 coupled to a disk 230in a spaced apart manner. As depicted, the fan blades 228 extendoutwardly from disk 230 generally along the radial direction R1. Eachfan blade 228 is rotatable relative to the disk 230 about a pitch axis Pby virtue of the fan blades 228 being operatively coupled to a suitableactuation member 232 configured to collectively vary the pitch of thefan blades 228 in unison. The fan blades 228, disk 230, and actuationmember 232 are together rotatable about the longitudinal axis 12 by LPshaft 224 across a power gear box 234. The power gear box 234 includes aplurality of gears for stepping down the rotational speed of the LPshaft 224 to a more efficient rotational fan speed.

Referring still to the exemplary embodiment of FIG. 3, the disk 230 iscovered by rotatable front hub 236 aerodynamically contoured to promotean airflow through the plurality of fan blades 228. Additionally, theexemplary fan section 202 includes an annular fan casing or outernacelle 238 that circumferentially surrounds the fan 226 and/or at leasta portion of the core turbine engine 204. It should be appreciated thatthe nacelle 238 may be configured to be supported relative to the coreturbine engine 204 by a plurality of circumferentially-spaced outletguide vanes 240. Moreover, a downstream section 242 of the nacelle 238may extend over an outer portion of the core turbine engine 204 so as todefine a bypass airflow passage 244 therebetween.

Further, the turbofan engine 200 depicted in FIG. 3 includes anaccessory gearbox 246 dedicated to the exemplary turbofan engine 200. Asis depicted schematically, the accessory gearbox 246 is mechanicallycoupled to a rotary component of the turbofan engine 200, or moreparticularly for the embodiment depicted, the accessory gearbox 246 ismechanically coupled to the LP shaft 224 of the turbofan engine 200.Accordingly, for the embodiment depicted, the accessory gearbox 246 isdriven by the LP shaft 224. Also for the embodiment depicted, theaccessory gearbox 246 includes an electrical machine (not shown), whichmay be configured as an electric motor and/or an electric generator.When the turbofan engine 200 is incorporated in the propulsion system100 described above with reference to FIGS. 1 and 2, the electricalmachine may thus include the electric generator 108. Such aconfiguration may allow for the accessory gearbox 246, including theelectrical machine, to generate electrical power from a rotation of theLP shaft 224.

It should be appreciated, however, that the exemplary turbofan engine200 depicted in FIG. 3 is by way of example only, and that in otherexemplary embodiments, the turbofan engine 200 may have any othersuitable configuration. Further, it should be appreciated, that in otherexemplary embodiments, the jet engines 102, 104 may instead beconfigured as any other suitable aeronautical engine, such as aturboprop engine, turbojet engine, internal combustion engine, etc.

Referring now to FIG. 4, a schematic, cross-sectional side view of anelectric propulsion engine in accordance with various embodiments of thepresent disclosure is provided. The electric propulsion engine depictedis mounted to an aircraft 10 at an aft end 18 of the aircraft 10 and isconfigured to ingest a boundary layer air. Accordingly, for theembodiment depicted, the electric propulsion engine is configured as aboundary layer ingestion (BLI), aft fan (referred to hereinafter as “BLIfan 300”). The BLI fan 300 may be configured in substantially the samemanner as the BLI fan 106 described above with reference to FIGS. 1 and2 and the aircraft 10 may be configured in substantially the same manneras the exemplary aircraft 10 described above with reference to FIGS. 1and 2. In other embodiments of the present disclosure, however, theelectric propulsion engine may instead be positioned at any othersuitable location on the aircraft 10, and may additionally oralternatively be configured to ingest freestream air.

As shown in FIG. 4, the BLI fan 300 defines an axial direction A2extending along a longitudinal centerline axis 302 that extendstherethrough for reference, as well as a radial direction R2 and acircumferential direction C2 (a direction extending about the axialdirection A2, not shown). Additionally, the aircraft 10 defines a meanline 15 extending therethrough.

In general, the BLI fan 300 includes a fan 304 rotatable about thecenterline axis 302 and a fan frame 308. The fan frame 308 is configuredfor mounting the BLI fan 300 to the aircraft 10, and for the embodimentdepicted generally includes an inner frame support 310, a plurality offorward support members 312, an outer nacelle 314, a plurality of aftsupport members 316, and a tail cone 318. As is depicted, the innerframe support 310 is attached to a bulkhead 320 of the fuselage 12. Theplurality of forward support members 312 are attached to the inner framesupport 310 and extend outward generally along the radial direction R2to the nacelle 314. The nacelle 314 defines an airflow passage 322 withan inner casing 324 of the BLI fan 300, and at least partially surroundsthe fan 304. Further, for the embodiment depicted, the nacelle 314extends substantially three hundred and sixty degrees (360°) around themean line 15 of the aircraft 10. The plurality of aft support members316 also extend generally along the radial direction R2 from, andstructurally connect, the nacelle 314 to the tail cone 318.

In certain embodiments, the forward support members 312 and the aftsupport members 316 may each be generally spaced along thecircumferential direction C2 of the BLI fan 300. Additionally, incertain embodiments the forward support members 312 may be generallyconfigured as inlet guide vanes and the aft support members 316 maygenerally be configured as outlet guide vanes. If configured in such amanner, the forward and aft support members 312, 316 may direct and/orcondition an airflow through the airflow passage 322 of the BLI fan 300.Notably, one or both of the forward support members 312 or aft supportmembers 316 may additionally be configured as variable guide vanes. Forexample, the support member may include a flap (not shown) positioned atan aft end of the support member for directing a flow of air across thesupport member.

It should be appreciated, however, that in other exemplary embodiments,the fan frame 308 may instead include any other suitable configurationand, e.g., may not include each of the components depicted and describedabove. Alternatively, the fan frame 308 may include any other suitablecomponents not depicted or described above.

The BLI fan 300 additionally defines a nozzle 326 between the nacelle314 and the tail cone 318. The nozzle 326 may be configured to generatean amount of thrust from the air flowing therethrough, and the tail cone318 may be shaped to minimize an amount of drag on the BLI fan 300.However, in other embodiments, the tail cone 318 may have any othershape and may, e.g., end forward of an aft end of the nacelle 314 suchthat the tail cone 318 is enclosed by the nacelle 314 at an aft end.Additionally, in other embodiments, the BLI fan 300 may not beconfigured to generate any measureable amount of thrust, and instead maybe configured to ingest air from a boundary layer of air of the fuselage12 of the aircraft 10 and add energy/speed up such air to reduce anoverall drag on the aircraft 10 (and thus increase a net thrust of theaircraft 10).

Referring still to FIG. 4, the fan 304 includes a plurality of fanblades 328 and a fan shaft 330. The plurality of fan blades 328 areattached to the fan shaft 330 and spaced generally along thecircumferential direction C2 of the BLI fan 300. As depicted, theplurality fan blades 328 are, for the embodiment depicted, at leastpartially enclosed by the nacelle 314.

In certain exemplary embodiments, the plurality of fan blades 328 may beattached in a fixed manner to the fan shaft 330, or alternatively, theplurality of fan blades 328 may be rotatably attached to the fan shaft330. For example, the plurality of fan blades 328 may be attached to thefan shaft 330 such that a pitch of each of the plurality of fan blades328 may be changed, e.g., in unison, by a pitch change mechanism (notshown). Changing the pitch of the plurality of fan blades 328 mayincrease an efficiency of the BLI fan 300 and/or may allow the BLI fan300 to achieve a desired thrust profile. With such an exemplaryembodiment, the BLI fan 300 may be referred to as a variable pitch BLIfan.

Moreover, for the embodiment depicted, the fan 304 is rotatable aboutthe centerline axis 302 of the BLI fan 300 by an electric motor 334.More particularly, for the embodiment depicted, the BLI fan 300additionally includes a power gearbox 336 mechanically coupled to theelectric motor 334, with the fan 304 mechanically coupled to the powergearbox 336. For example, for the embodiment depicted, the fan shaft 330extends to and is coupled to the power gearbox 336, and a driveshaft 332of the electric motor 334 extends to and is also coupled to the powergearbox 336. Accordingly, for the embodiment depicted, the fan 304 isrotatable about the central axis 302 of the BLI fan 300 by the electricmotor 334 through the power gearbox 336.

The power gearbox 336 may include any type of gearing system foraltering a rotational speed between the driveshaft 332 and the fan shaft330. For example, the power gearbox 336 may be configured as a star geartrain, a planetary gear train, or any other suitable gear trainconfiguration. Additionally, the power gearbox 336 may define a gearratio, which as used herein, refers to a ratio of a rotational speed ofthe driveshaft 332 to a rotational speed of the fan shaft 330.

Referring still to the exemplary embodiment of FIG. 4, the electricmotor 334 is located forward of the power gearbox 336, and the powergearbox 336 is, in turn, located forward of the fan 304. Notably, theelectric motor 334 is in electrical communication with a power sourcevia an electrical line 338. In certain exemplary embodiments, the BLIfan 300 may be configured with a gas-electric propulsion system, such asthe gas-electric propulsion system 100 described above with reference toFIGS. 1 and 2. In such an embodiment, the electric line 338 may beconfigured as part of the electrical communication bus 111, such thatthe electric motor 334 may receive power from one or both of an energystorage device or an electric generator—such as the energy storagedevice 110 or electric generators 108 of FIGS. 1 and 2, and/or from theelectrical machine of the accessory gearbox 246 of the turbofan engine200.

Furthermore, as is depicted schematically in FIG. 4, the BLI fan 300additionally includes a bearing 340 supporting rotation of the fan 304.More particularly, the exemplary BLI fan 300 of FIG. 4 includes abearing 340 directly supporting the fan shaft 330 of the fan 304.Although not depicted, the bearing 340 may be supported by one or morestructural members of the BLI fan 300. Additionally, as will bediscussed in greater detail below, the BLI fan 300 includes an accessorygearbox 342 dedicated to the BLI fan 300 and a thermal managementsystem. The thermal management system may be configured at leastpartially with (e.g., included at least partially within) the accessorygearbox 342 and may be configured for providing lubrication oil to (andfrom) the bearing 340, and further for managing a temperature of suchlubrication oil and bearing 340.

Referring now to FIG. 5, providing a close-up, schematic,cross-sectional view of the exemplary BLI fan 300 of FIG. 4, the thermalmanagement system and other aspects of the BLI fan 300 are depicted. Forthe exemplary embodiment depicted, the bearing 340 is configured as asingle, roller element bearing directly supporting the fan shaft 330.However, in other embodiments, the bearing 340 may include any othersuitable type of oil-lubricated bearing, such as a ball bearing, taperedroller bearing, etc. Additionally, in still other embodiments, thebearing 340 may additionally or alternatively include an air bearing,and further may include a plurality of bearings supporting rotation ofthe fan 304, and more particularly, the fan shaft 330.

The bearing 340 is supported by a static structural member 344 of theBLI fan 300, and is enclosed within a sump 346 of the BLI fan 300. Thesump 346, as will be discussed in greater detail below, is configured tocollect lubrication oil provided to the bearing 340. The lubrication oilis provided to the bearing 340 for, e.g., lubricating the bearing 340and regulating a temperature of the bearing 340. The exemplary sump 346depicted includes a forward sump wall 348 and an aft sump wall 350.Additionally, the fan shaft 330 includes a forward seal 352 configuredto form a seal with the forward sump wall 348 and an aft seal 354configured to form a seal with the aft sump wall 350. It should beappreciated, however, that in other embodiments, the sump 346 enclosingthe bearing 340 have any other suitable configuration capable ofcollecting lubrication oil provided to the bearing 340.

As mentioned above, the exemplary BLI fan 300 depicted includes athermal management system. Specifically, the exemplary thermalmanagement system includes a lubrication oil circulation assembly and aheat exchanger 356 thermally connected to the lubrication oilcirculation assembly. The lubrication oil circulation assembly isconfigured for providing the bearing 340 with the lubrication oil, andin certain embodiments, includes a lubrication oil supply pump 358 and alubrication oil scavenge pump 360. Notably, for the exemplary embodimentdepicted, the lubrication oil supply pump 358 and lubrication oilscavenge pump 360 are included within and driven by the accessorygearbox 342. However, in other embodiments, the lubrication oil supplypump 358 and lubrication oil scavenge pump 360 may instead be separatefrom the accessory gearbox 342 and, e.g., mechanically coupled to theaccessory gearbox 342 in a suitable manner. Moreover, although notdepicted, the lubrication oil circulation assembly may additionallyinclude, e.g., a lubrication oil tank and/or other features not depictedor described herein.

The lubrication oil supply pump 358 is fluidly connected to alubrication oil supply line 362 for providing lubrication oil to thebearing 340 within the sump 346. Similarly, the lubrication oil scavengepump 360 is fluidly connected to a lubrication oil scavenge line 364 forscavenging out lubrication oil from within the sump 346. The heatexchanger 356 is positioned in the flowpath of the lubrication oilscavenge line 364 for cooling the lubrication oil flowing therethrough.Particularly for the embodiment depicted, the heat exchanger 356 islocated between two segments of the lubrication oil scavenge line 364and is configured as an air cooled oil cooler. Accordingly, an airflowthrough the air cooled oil cooler may accept heat from the scavengedlubrication oil flowing through the lubrication oil scavenge line 364and heat exchanger 356. Additionally for the embodiment depicted, theBLI fan 300 includes a blower 366, driven by the accessory gearbox 342,providing an airflow through the air cooled oil cooler. The blower 366is in airflow communication with an inlet 368 defined by an exteriorsurface 38 of the fuselage 12 via an inlet line 370. After flowingthrough the heat exchanger 356, the heated air is exhausted to anexterior location through an outlet 372 defined by the outer surface 38of the fuselage 12 via an outlet line 374.

It should be appreciated, however, that in other exemplary embodimentsthe airflow through the heat exchanger 356 may be ducted in any othersuitable manner and further that the heat exchanger 356 may bepositioned at any other suitable location and/or integrated into one ormore additional components of the BLI fan 300. For example, referringnow briefly to FIG. 6, a close-up, side, schematic view of a BLI fan 300in accordance with another exemplary embodiment of the presentdisclosure is depicted. The exemplary BLI fan 300 depicted in FIG. 6 maybe configured in substantially the same manner as exemplary BLI fan 300depicted in FIG. 5, and accordingly, the same or similar numbers mayrefer to the same or similar parts. However, for the embodiment of FIG.6, the heat exchanger 356 is in airflow communication with a cool airsource at a location downstream of the fan 304 (e.g., at a locationproximate the nozzle 326) through an inlet line 371. For the embodimentdepicted, the inlet line 371 extends through the forward support member312 and along the outer nacelle 314 to the location downstream of thefan 304. The airflow is pulled through the heat exchanger 356 via thepump 366 and through an outlet line 373 to an outlet 375 at a locationupstream of the fan 304. Such a configuration may provide air withhigher energy into the air flowpath of the fan 304. Notably, however, infurther exemplary embodiments, the airflow through the outlet line 373may instead be ducted to an overboard location that is not locatedupstream of the fan 304.

Further, as is also depicted schematically in FIG. 6, the heat exchanger356 may be positioned at any other suitable location and/or integratedinto one or more additional components of the BLI fan 300. For example,in certain embodiments, the thermal management system may include a heatexchanger 356A integrated into the outer surface 38 of the fuselage 12,a heat exchanger 356B integrated into the forward support member312/inlet guide vane, a heat exchanger 356C integrated into aft supportmember 216/outlet guide vane, etc. Moreover, although not depicted, itshould be appreciated that in still other embodiments the heat exchanger356 may instead be positioned in, e.g., the flowpath of the lubricationoil supply line 362 or at any other suitable location.

Referring again to the embodiment of FIG. 5, the BLI fan 300additionally includes a pressurization pump 376 for maintaining aninterior cavity of the sump 346 (or alternatively a cavity surroundingthe sump 346) at a desired pressure. Maintaining the interior cavity ofthe sump 346 at a desired pressure may assist in preventing an amount oflubrication oil from leaking therefrom. For example, the pressurizationpump 376 may be a ventilation pump configured to pump air out of thesump 346 to maintain a higher pressure surrounding the sump 346 thanwithin the sump 346. As is depicted schematically, the accessory gearbox342 additionally drives the pressurization pump 376. Notably, for theembodiment depicted, the pressurization pump 376 is in airflowcommunication with a sump 346 pressurization line 378 extending to, andin airflow communication with, the sump 346.

Furthermore, the exemplary accessory gearbox 342 is powered by theelectric motor 334 of the BLI fan 300. More particularly, for theembodiment depicted, the accessory gearbox 342 is mechanically coupledto and driven by the electric motor 334 through a geartrain 380.Additionally, as previously discussed, the exemplary electric motor 334depicted is in electrical communication with a power source through theelectrical line 338.

The accessory gearbox 342 depicted in FIG. 5 is dedicated to the BLI fan300. Additionally, the accessory gearbox 342 includes a secondaryelectrical machine 382. The secondary electrical machine 382 may be, incertain embodiments, an electric generator including a stator 384 and arotor 386. The accessory gearbox 342 may be configured to rotate therotor 386 of the secondary electrical machine 382, such that thesecondary electrical machine 382 may generate an amount of electricalpower. The electrical power generated by the secondary electricalmachine 382 may be provided to, e.g., the aircraft 10 for poweringcertain low power level systems of the aircraft 10 (e.g., avionics,emergency hydraulics/control surfaces, etc.). For example, in a failurescenario, the BLI fan 300 may be utilized essentially as a ram airturbine to provide auxiliary power to the aircraft 10 using thesecondary electrical machine 382 of the accessory gearbox 342. Such aconfiguration may be more advantageous than using power directly from agenerator producing relatively high voltage electric power for powering,e.g., the electric motor 334 (and including a variety of powerelectronics for stepping down such high voltage electric power).

Furthermore, it should be appreciated that in still other exemplaryembodiments, the thermal management system of the exemplary BLI fan 300may share certain components or functions with, e.g., one or more of thegas turbine engines of an aircraft 10 with which the BLI fan 300 isinstalled. For example, referring now to FIGS. 7 and 8, a propulsionsystem 100 including a BLI fan 300 in accordance with another exemplaryembodiment of the present disclosure is depicted. FIG. 7 provides aclose-up, side, schematic view of the exemplary BLI fan 300, and FIG. 8provides a schematic view of the exemplary propulsion system 100.

Referring first to FIG. 7, the exemplary BLI fan 300 may be configuredin substantially the same manner as exemplary BLI fan 300 depicted inFIG. 5, and accordingly, the same numbers may refer to the same orsimilar parts. Additionally, however, the exemplary BLI fan 300 of FIG.7 includes a thermal management system having a thermal fluidcirculation assembly in thermal communication with at least one of anelectric motor 334 of the BLI fan 300 or a bearing 340/bearing sump 346of the BLI fan 300. Particularly, for the embodiment depicted, thethermal fluid circulation assembly is a lubrication oil circulationassembly in thermal communication with both the electric motor 334 andthe bearing 340/bearing sump 346 of the BLI fan 300. Specifically, theexemplary lubrication oil circulation assembly is configured forproviding a lubrication oil to, and scavenging lubrication oil from, thebearing 340 and the sump 346. Additionally, for the embodiment depicted,a supply line 362 of the thermal management system is further configuredin thermal communication with the electric motor 334 of the BLI fan 300for removing heat from the electric motor 334.

As with the exemplary lubrication oil circulation assembly of thethermal management system described above with reference to FIG. 5, theexemplary lubrication oil circulation assembly includes a lubricationoil supply pump 358 and a lubrication oil scavenge pump 360. Thelubrication oil supply and scavenge pumps 358, 360 are positioned withinand driven by an accessory gearbox 342. Notably, however, in otherembodiments, the circulation assembly may have any other suitableconfiguration.

Further, for the embodiment of FIGS. 7 and 8, the thermal managementsystem shares cooling functions with a main aircraft engine, such as anunder-wing mounted aircraft engine. More specifically, referring nowparticularly to FIG. 8, the scavenge line 364 for the embodimentdepicted is routed forward, away from the BLI fan 300. Additionally, forthe exemplary propulsion system 100 depicted, the propulsion system 100includes a first engine, such as first engine 102, and a second engine,such as second engine 104. The first engine 102 includes a first thermalmanagement system 392 having a first heat exchanger 393, and the secondengine 104 includes a second thermal management system 394 having asecond heat exchanger 395, via a parallel flow configuration. As isdepicted, the lubrication oil circulation assembly of the exemplarythermal management system of the BLI fan 300 is in thermal communicationwith at least one of the first heat exchanger 393 of the first thermalmanagement system 392 of the first engine 102, or the second heatexchanger 395 of the second thermal management system 394 of the secondengine 104. More specifically, for the embodiment depicted, the scavengeline 364 of lubrication oil circulation assembly of the BLI fan 300 isin thermal communication with both the first heat exchanger 393 and thesecond heat exchanger 395. In certain exemplary embodiments the firstheat exchanger 393 may be an intermediate heat exchanger for positioningthe thermal management system of the BLI fan 300 in thermalcommunication with the thermal management system 392 of the first engine102, and similarly, the second heat exchanger 395 may be an intermediateheat exchanger for positioning the thermal management system of the BLIfan 300 in thermal communication with the thermal management system 394of the second engine 104. Accordingly, with such an exemplaryembodiment, a leak in the thermal management system of the BLI fan 300would not necessitate a shutting down of one or both of the firstthermal management system 392 or the second thermal management system394.

It should be appreciated, however, that in other exemplary embodiments,one or both of the first heat exchanger 393 or second heat exchanger 395may be a heat exchanger utilized for reducing a temperature of both thethermal fluid/lubrication oil through the scavenge line 364 and athermal fluid/lubrication oil through the first thermal managementsystem 392 or second thermal management system 394. For example, incertain exemplary embodiments, the one or both of the first heatexchanger 393 or second heat exchanger 395 may be configured as afuel-oil heat exchanger, a bypass air heat exchanger, or any othersuitable heat exchanger.

After having been cooled by the first and second heat exchangers 393,395 of the first and second thermal management systems 392, 394,respectively, the lubrication oil is pumped back through respectivereturn portions 396 of the scavenge line 364 towards the BLI fan 300.

As is depicted, the exemplary propulsion system 100 of FIG. 8 is ahybrid-electric propulsion system 100, similar to the hybrid-electricpropulsion system 100 described above with reference to FIGS. 1 and 2.Accordingly, the exemplary propulsion system 100 generally includes afirst electric generator 108A coupled to and driven by the first engine102 and a second electric generator 108B coupled to and driven by thesecond engine 104. For the exemplary propulsion system 100 depicted, thefirst and second electric generators 108A, 108B are electricallyconnected to the electric motor 334 of the BLI fan 300 via an electriccommunication bus 111. Notably, although for the embodiment depicted theelectric motor 334 is depicted as a single motor electrically connectedto both the first and second electric generators 108A, 108B, in otherembodiments, the electric motor 334 may instead include a plurality ofcoaxially mounted electric motors. For example, in certain embodiments,the electric motor 334 may include a first electric motor electricallyconnected to the first electric generator 108A through the electriccommunication bus 111 and a second, coaxially mounted electric motorelectrically connected to the second electric generator 108B alsothrough the electric communication bus 111.

Depending on the electrical demands for the BLI fan 300, it may benecessary to transmit relatively high levels of electric power throughthe electric communication bus 111. As will be appreciated, transmittingsuch relatively high levels of electric power may generate anundesirable amount of heat in the electric communication bus, and moreparticularly, in the transmission lines 338 of the electriccommunication bus 111. Accordingly, for the embodiment depicted, theelectric communication bus includes a first, upstream juncture box 397proximate the first electric generator 108A and a second upstreamjuncture box 398 proximate the second electric generator 108B. The firstupstream juncture box 397 is electrically connected to the firstelectric generator 108A and fluidly connected to the return portion 396of the lubrication oil scavenge line 364, downstream of the first heatexchanger 393. Similarly, the second upstream juncture box 398 iselectrically connected to the second electric generator 108B and fluidlyconnected to the return portion 396 of the lubrication oil scavenge line364, downstream of the second heat exchanger 395. Moreover, the electriccommunication bus 111 includes a downstream juncture box 399 positionedproximate the electric motor 334. The downstream juncture box 399electrically connects to the electric motor 334 and fluidly connects tothe lubrication oil circulation assembly, or more particularly, thelubrication oil scavenge pump 360.

Further, as is depicted schematically, the return portions 396 of thescavenge line 364—extending between the first upstream juncture box 397and the downstream juncture box 399 and between the second upstreamjuncture box 398 and the downstream juncture box 399—are configured tocool the transmission lines 338 of the electric communication bus 111extending between the electric generators 108A, 108B and the electricmotor 334. Specifically, the transmission lines 338 may extend coaxiallywithin the return portions 396 of the lubrication oil scavenge line 364,surrounded by a cooled lubrication oil flowing therethrough to providethermal control of the transmission lines 338. Such a configuration mayallow for more efficient electrical communication between the electricgenerators 108A, 108B and the electric motor 334.

It should be appreciated that although for the embodiment depicted thethermal management system of the BLI fan 300 is thermally connected toboth the electric motor 334 and the bearing 340/sump 346, in otherembodiments, the thermal management system of the BLI fan 300 may not bethermally connected to both. Moreover, although the thermal connectionto the electric motor 334 is shown as a plurality of coils around themotor 334, in other embodiments, the thermal management system mayinstead be thermally connected in any other suitable manner.

Referring now to FIG. 9, a close-up, side, schematic view of a BLI fan300 in accordance with another exemplary embodiment of the presentdisclosure is depicted. The exemplary BLI fan 300 depicted in FIG. 9 maybe configured in substantially the same manner as exemplary BLI fan 300depicted in FIG. 5, and accordingly, the same or similar numbers mayrefer to the same or similar parts.

As is depicted, the BLI fan 300 of FIG. 9 generally includes an electricmotor 334 drivingly connected to a fan 304 through a power gearbox 342.The fan 304 includes a fan shaft 330, which is supported by a bearing340 attached to a structural member 344 of the BLI fan 300. The bearing340 is enclosed within a sump 346 defined by a forward sump wall 348 andan aft sump wall 350. The BLI fan 300 additionally includes a thermalmanagement system for providing lubrication oil to, and scavenginglubrication oil from, the bearing 340 and the sump 346. As with theexemplary thermal management system described above with reference toFIG. 5, the exemplary thermal management system depicted in FIG. 9additionally includes a lubrication oil circulation assembly, thelubrication oil circulation assembly including lubrication oil supplypump 358 and a lubrication oil scavenge pump 360. Also for theembodiment depicted, the lubrication oil supply and scavenge pumps 358,360 are positioned within and driven by an accessory gearbox 342.

Additionally, the thermal management system of the BLI fan 300 includesa heat exchanger 356 in thermal communication with the lubrication oilcirculation assembly. However, for the embodiment depicted, the heatexchanger 356 is instead configured as a liquid to lubrication oil heatexchanger. For example, in certain exemplary embodiments, the heatexchanger 356 may be configured as part of a thermal management bus 388of the aircraft 10. The thermal management bus 388 may thermally connectvarious heat sources and heat sinks of the aircraft through a commonthermal fluid flowing therethrough. The thermal fluid may be an oil, oralternatively may be a cryogenic fluid or phase change fluid, forexample when the thermal management bus 388 operates under arefrigeration cycle. Accordingly, the heat exchanger 356 depicted inFIG. 9 may be configured as a thermal fluid to lubrication oil heatexchanger.

Referring still to FIG. 9, the exemplary accessory gearbox 342 depictedis not mechanically coupled to or driven directly by the electric motor334. Instead, for the embodiment depicted, the accessory gearbox 342 iselectrically connected to a power source through an electric line 390.The electric line 390 may be electrically connected to, e.g., theelectrical communication bus 111 described above with reference to FIGS.1 and 2. Accordingly, in certain embodiments, the electric motor 334 andthe accessory gearbox 342 may each be driven by an electric generatordriven by a gas turbine engine, such as one or both of the jet engines102, 104. Additionally, or alternatively, the exemplary accessorygearbox 342 of the BLI fan 300 depicted in FIG. 9 may be configured toreceive electrical power from an electrical machine of a separate gasturbine engine. For example, referring to FIG. 3, the accessory gearbox342 of the BLI fan 300 may be in electrical communication with theelectrical machine (which may be configured as an electric generator) ofthe accessory gearbox 246 of the turbofan engine 200.

It should be appreciated, however, that in other exemplary embodiments,the BLI fan 300 may not include the accessory gearbox 342. For example,referring now briefly to FIG. 10, a close-up, side, schematic view of aBLI fan 300 in accordance with another exemplary embodiment of thepresent disclosure is depicted. The exemplary BLI fan 300 depicted inFIG. 10 may be configured in substantially the same manner as exemplaryBLI fan 300 depicted in FIG. 9, and accordingly, the same or similarnumbers may refer to the same or similar parts. However, for theembodiment of FIG. 6, each of the accessory systems (e.g., thelubrication oil supply and scavenge pumps 358, 360, the pressurizationpump 376, and the secondary electrical machine 382) are each separatelypowered by an electric power source of the aircraft via an electric line390. For example, for the embodiment depicted, each of the plurality ofaccessory systems include a dedicated electric motor for powering theaccessory system in electrical communication with power source viaelectric line 390. It should be appreciated, however, that in stillother exemplary embodiments, one or more of the plurality of accessorysystems may additionally or alternatively be powered by the electricmotor 334, e.g., one or more of the plurality of accessory systems mayadditionally or alternatively be independently mechanically coupled tothe electric motor 334.

A propulsion system including an electric propulsion engine inaccordance with one or more embodiments of the present disclosure mayallow for a more independently configured electrical propulsion engineless dependent on secondary/accessory systems of other propulsionengines. For example, a propulsion system including an electricpropulsion engine in accordance with one or more embodiments of thepresent disclosure may allow for the electric propulsion engine toinclude a dedicated thermal management system, accessory gearbox, andother secondary systems, such that the engine is less dependent on otheraccessory systems of the aircraft. Such a configuration may allow forthe electric propulsion engine to be located at, e.g., remote locationson the aircraft, such as at an aft end of the aircraft.

Referring now to FIGS. 10 and 11, close-up, side, schematic views of BLIfans 300 in accordance with other exemplary embodiments of the presentdisclosure are depicted. The exemplary BLI fans 300 depicted in FIGS. 10and 11 may be configured in substantially the same manner as exemplaryBLI fan 300 depicted in FIG. 5, and accordingly, the same or similarnumbers may refer to the same or similar parts.

As is depicted, the BLI fans 300 of FIGS. 10 and 11 each generallyinclude an electric motor 334 drivingly connected to a fan 304 through apower gearbox 336. The fan 304 is rotatable about a centerline axis 302.The BLI fans 300 of FIGS. 10 and 11 each also include a fan frame 308,the fan frame 308 generally including an inner frame support 310, aplurality of forward support members 312, an outer nacelle 314, aplurality of aft support members 316, and a tail cone 318. As isdepicted, the inner frame support 310 is attached to a bulkhead 320 ofthe fuselage 12. The plurality of forward support members 312 areattached to the inner frame support 310 and extend outward generallyalong the radial direction R2 to the nacelle 314. The nacelle 314defines an airflow passage 322 with an inner casing 324 of the BLI fan300, and at least partially surrounds the fan 304.

Moreover, for the embodiments depicted, each of the BLI fans 300depicted in FIGS. 10 and 11 include a cooling system 400 operable withan airflow 402 over the aft end 18 of the aircraft 10 for cooling one ormore components of the respective BLI fan 300.

Referring particularly to FIG. 11, the cooling system 400 is configuredto cool the electric motor 334 during operation BLI fan 300. Morespecifically, for the embodiment depicted, the cooling system 400includes a closed loop 404 configured to flow a thermal transfer fluidtherethrough. In certain embodiments, the thermal transfer fluid may bea lubrication oil, a refrigerant, or any other suitable fluid capable oftransferring thermal energy. Additionally, the closed loop 404 of theexemplary cooling system 400 depicted forms a plurality of thermaltransfer ducts 406 positioned in thermal communication with the electricmotor 334. For example, the thermal transfer ducts 406 may, as in theembodiment depicted, extend around an exterior surface of the electricmotor 334. Accordingly, for the embodiment depicted, the thermaltransfer ducts 406 may be referred to as coils. Additionally, oralternatively, the thermal transfer ducts 406 may include one or moreportions extending through or into an interior portion of the electricmotor 334. For example, the thermal transfer ducts 406 may include oneor more sealed passageways or microchannels extending through theelectric motor 334. In still other embodiments, the thermal transferducts 406 may additionally or alternatively include heat pipes. Theplurality of thermal transfer ducts 406 are configured to reduce atemperature of the electric motor 334 during operation the BLI fan 300by accepting heat from the electric motor 334 and transferring such heatto the thermal transfer fluid flowing therethrough. The exemplarycooling system 400 depicted further includes a heat exchanger in thermalcommunication with the thermal transfer fluid within the closed loop 404and with the airflow 402 over the aft end 18 of the aircraft 10. Theheat exchanger is configured for removing heat from the thermal transferfluid within the closed loop 404. More specifically, the exemplarycooling system 400 depicted includes a first support member heatexchanger 408, a nacelle heat exchanger 410, and a second support memberheat exchanger 412. The first and second support member heat exchangers408, 412 are integrated into a surface of respective forward supportmembers 312. Similarly, the nacelle heat exchanger 410 is integratedinto a surface of the outer nacelle 314. Particularly for the embodimentdepicted, the outer nacelle 314 includes a forward tip 414 and thenacelle heat exchanger 410 is integrated into a surface of the forwardtip 414 of the outer nacelle 314. Such a configuration may allow for thenacelle heat exchanger 410 to provide de-icing benefits to the outernacelle 314 during operation. Additionally, although not depicted, incertain embodiments, the nacelle heat exchanger 410 may extend along anentire circumference of the outer nacelle 314 (i.e., may extendsubstantially continuously along the circumferential direction C2).

Referring still to FIG. 11, the exemplary aircraft 10 includes astabilizer and the exemplary cooling system 400 depicted furtherincludes a heat exchanger configured for integration into thestabilizer. More particularly, the exemplary aircraft 10 depictedincludes a vertical stabilizer 30 at the aft end 18 of the aircraft 10and the cooling system 400 depicted further includes a stabilizer heatexchanger 416 integrated into a surface of the vertical stabilizer 30for transferring heat to the airflow 402 over the aft end 18 of theaircraft 10. As is depicted, the closed loop 404 of the cooling system400 branches off downstream of the thermal transfer ducts 406 to extendto the stabilizer heat exchanger 416 and returns at a location upstreamof the thermal transfer ducts 406.

In order to provide a flow of the thermal transfer fluid through theclosed loop 404 of the cooling system 400, the exemplary cooling system400 further includes a pump. More specifically, the cooling system 400includes a pump 418 positioned within and driven by an accessory gearbox342 of the BLI fan 300. The exemplary accessory gearbox 342 depicted isdedicated to the BLI fan 300. Additionally, for the embodiment depicted,the accessory gearbox 342, and thus the pump 418, is driven by theelectric motor 334. However, in other embodiments, the accessory gearbox342 may instead be powered directly by a suitable electrical powersource of the aircraft 10 and/or one or more aircraft engines.Additionally, in still other embodiments, the pump 418 may be astandalone pump mechanically or electrically powered by any suitablesource.

It should be appreciated that although for the embodiment depicted thepump 418 and closed loop 404 of the cooling system 400 are depictedbeing independent of any other accessory system, in other embodiments,the pump 418 and closed loop 404 may be operable with one or more of theexemplary thermal management systems described above with reference toFIGS. 5 through 9. For example, in certain embodiments, the closed loop404 may be fluidly connected with (or simply an extension of) one of thelubrication oil supply line 362 or lubrication oil scavenge line 364 (inwhich case, the pump 418 may be the same, or operable with, one or bothof the lubrication oil supply or scavenge pumps 358, 360 (see, e.g.,FIG. 5).

During operation of the BLI fan 300, and the cooling system 400, thepump 418 may pressurize a thermal transfer fluid within the closed loop404, generating a flow of the thermal transfer fluid through the closedloop 404. The thermal transfer fluid may flow through the thermaltransfer ducts 406, where the thermal transfer fluid accepts heat fromthe electric motor 334, reducing a temperature of the electric motor334. The thermal transfer fluid may then flow towards the plurality ofheat exchangers. A first portion of the thermal transfer fluid may flowfrom the thermal transfer ducts 406 through the first support memberheat exchanger 408, through the nacelle heat exchanger 410 (and aroundthe outer nacelle 314), through the second support member heat exchanger412, and back towards the pump 418. A second portion of the thermaltransfer fluid may simultaneously flow from the thermal transfer ducts406 through the stabilizer heat exchanger 416, and back towards the pump418. A temperature of the first and second portions of the thermaltransfer fluid may be reduced when flowing through the various heatexchangers, by exchanging heat with the airflow 402 over the aft and theaircraft 10.

It should be appreciated, however, that in other embodiments, thecooling system 400 may have any other suitable configuration. Forexample, in other embodiments, the cooling system 400 may not includeeach of the various heat exchangers depicted in FIG. 11. Additionally,or alternatively, the exemplary cooling system 400 may include any othersuitable configuration of heat exchanger(s). For example, in otherembodiments, the cooling system 400 may include one or more heatexchangers integrated into a surface 38 of the fuselage 12, integratedinto a surface of the tail cone 318, integrated into a surface of an aftsupport member 316, or positioned at any other suitable location fortransferring heat to the airflow 402 over the aft end 18 of the aircraft10. Further still, in other embodiments, the cooling system 400 mayadditionally include any other suitable type of heat exchangers, such asa fuel-oil heat exchanger, an oil-oil heat exchanger, a hydraulicfluid-oil heat exchanger, a hydraulic fluid-oil heat exchanger, etc.

Moreover, in still other exemplary embodiments, the closed loop 404 ofthe exemplary cooling system 400 may be configured to provide a flow ofthe thermal transfer fluid through one or more heat exchangers in aparallel flow configuration, in a series flow configuration, or in acombination thereof (such as in the embodiment depicted).

Referring now particularly to the exemplary BLI fan 300 of FIG. 12, thecooling system 400 is similarly operable with an airflow 402 over theaft end 18 of the aircraft 10 and configured to cool the electric motor334 during operation of the BLI fan 300.

However, for the embodiment depicted, the exemplary cooling system 400depicted is a direct, air-cooled cooling system. For example, theexemplary cooling system 400 generally includes a cooling air duct 420defining an inlet 422 and an outlet, and extending at least partiallyover or adjacent to the electric motor 334. The inlet 422 is configuredto receive at least a portion of the airflow 402 over the aft end 18 ofthe aircraft 10 as a cooling airflow 426. More specifically, for theembodiment depicted, the inlet 422 of the cooling air duct 420 ispositioned on a fuselage 12 of the aircraft 10, at a location upstreamfrom, and forward of, the fan 304. Accordingly, the inlet 422 is inairflow communication with a location outside of the aircraft 10 andforward of the fan 304. Further, for the embodiment depicted, the inlet422 is also located forward of the electric motor 334. Although notdepicted, the exemplary cooling system 400 may include a fixed orvariable geometry scoop or lip at the inlet 422 extending outwardly intothe airflow 402 for ensuring a desired amount of such airflow 42 isreceived as cooling airflow 426 in the cooling air duct 420.Additionally, in certain embodiments, the cooling system 400 may includean air filter mechanism 427 extending across the air duct 420 forfiltering any particulates or other matter from the cooling airflow 426within the cooling air duct 420.

The airflow 402 over the aft end 18 of the aircraft 10 may be receivedin the cooling air duct 420 through the inlet 422 of the cooling airduct 420 and provided to a cavity 428 defined by the cooling air duct420, the cavity 428 thermally connecting the cooling airflow 426 withinthe cooling air duct 420 to the electric motor 334. More specifically,the exemplary cavity 428 depicted surrounds at least a portion of theelectric motor 334 and allows for the cooling airflow 426 through thecooling air duct 420 to be exposed directly to at least a portion of theelectric motor 334. The cooling airflow 426 may accept heat from theelectric motor 334, reducing a temperature of the electric motor 334. Incertain embodiments, the cooling airflow 426 may be directed to aninterior of the electric motor 334 to specifically cool certaincomponents of the electric motor 334 (not shown; e.g., a rotor and/or astator). However, in other embodiments, the cooling airflow 426 may belimited to the exterior of the electric motor 334. In certainembodiments, the cooling system 400 and/or the electric motor 334 mayinclude features for enhancing a heat transfer from the electric motor334 to the cooling airflow 426. For example, although not depicted, theelectric motor 334 may include one or more fins, pins, turbulators, etc.

The cooling airflow 426, after having received heat from the electricmotor 334, may then continue through the cooling air duct 420 to theoutlet. For the embodiment depicted, the cooling air duct 420 includes afirst outlet 430 and a second outlet 432. The first outlet 430 ispositioned on one of the forward support members 312 and is configuredto provide at least a portion (e.g., a first portion 434) of the coolingairflow 426 through the cooling air duct 420 to the fan 304. Notably,inclusion of the outlet 430 on the forward support member 312 (which maybe shaped as an airfoil) may allow for providing an amount of controlover the airflow 426 through the air duct 420. For example, placement ofthe outlet 430 on the forward support member 312 may allow for inducingthe airflow 426 through the air duct 420. Additionally, the exemplarycooling air duct 420 includes the second outlet 432 located on aradially outer side of the outer nacelle 314. Accordingly, for theembodiment depicted, the cooling air duct 420 additionally extendsthrough the forward support member 312 to the outer nacelle 314 andexhausts at least a portion (e.g., a second portion 436) of the coolingairflow 426 through the outer nacelle 314. Notably, with such aconfiguration, the second portion 436 of the cooling airflow 426 may beat a relatively high pressure compared to a boundary layer air over theradially outer side of the outer nacelle 314. Accordingly, exhaustingthe second portion 436 of air to through the outer nacelle 314 mayreduce a drag generated by the outer nacelle 314.

Furthermore, the exemplary embodiment depicted in FIG. 12 includes a fan438 positioned at least partially within the cooling air duct 420 forassisting in providing an airflow through the cooling air duct 420. Thefan 438 of the exemplary cooling system 400 depicted in FIG. 12 ismechanically driven by the electric motor 334 through a geartrain.However, in other embodiments, the fan 438 may instead be powered by anysuitable mechanical or electrical power source. Alternatively still, inother embodiments, the cooling system 400 may not include a fan, andinstead may rely on a pressure differential between the inlet 422 of thecooling duct 420 and the outlet (e.g., the first outlet 430 or secondoutlet 432) of the cooling duct 420 to generate the flow of coolingairflow 426 therethrough.

Notably, for the embodiment of FIG. 12, the inlet 422 is depicted as asingle, relatively large inlet, and the outlets are each depicted as asingle, relatively large outlet. However, in other embodiments, theinlet 422 may instead be formed of a plurality of relatively smallopenings or apertures on the fuselage 12 of the aircraft 10 and,similarly, the one or both of the outlets 430, 432 may be configured asa plurality of relatively small openings or apertures in, e.g., one ormore of the support members 312, the outer nacelle 314, etc. Further,although positioned on an under side of the fuselage 12 of the aircraft10 depicted in FIG. 12, in other embodiments, the inlet 422 mayadditionally or alternatively be positioned at any other suitablelocation on the fuselage 12 of the aircraft 10 (e.g., a top side, a portside, and/or a starboard side), or elsewhere. For example, in otherembodiments, the inlet 422 of the cooling air duct 420 may be in airflowcommunication with a location downstream of the fan 304 of the BLI fan300 (e.g., at the nozzle section 326), so as to receive a relativelyhigh pressure air for generating an airflow through the cooling air duct420. Further, although the cooling air duct 420 depicted include a firstoutlet 430 on a structural member and a second outlet 432 on the outernacelle 314, in other embodiments, the cooling air duct 420 may onlyinclude outlets on one or more structural members, on the outer nacelle314, or at any other suitable location.

Moreover, in other embodiments, the cooling system 400 may includeaspects of the exemplary cooling system 400 described above withreference to FIG. 11, in addition to aspects of the exemplary coolingsystem 400 described above with respect to FIG. 12. For example, inother exemplary embodiments, the cooling system 400 may include both aclosed loop 404 (and, e.g. one or more heat exchangers, coils 406, etc.)and a cooling air duct 420 providing a cooling airflow over the electricmotor 334.

Moreover, still, in other embodiments, the exemplary cooling system 400described with reference to FIG. 12 may be utilized in combination withone or more of the exemplary thermal management systems described abovewith reference to FIGS. 5 through 9. For example, in certain exemplaryembodiments, the cooling airflow 426 in the duct 420 may be in thermalcommunication with one or more of the heat exchangers of the exemplarythermal management systems described above with reference to FIGS. 5through 9.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A propulsion system for an aircraft having an aftend, the propulsion system comprising: an electric propulsion enginedefining a central axis, the electric propulsion engine comprising anelectric motor; a fan rotatable about the central axis of the electricpropulsion engine by the electric motor; a bearing supporting rotationof the fan; and a thermal management system comprising a lubrication oilcirculation assembly for providing the bearing with lubrication oil; anda heat exchanger thermally connected to the lubrication oil circulationassembly.
 2. The propulsion system of claim 1, wherein the lubricationoil circulation assembly comprises a lubrication oil supply pump and alubrication oil scavenge pump.
 3. The propulsion system of claim 1,further comprising: a sump enclosing the bearing, wherein thelubrication oil circulation assembly is fluidly connected to the sump.4. The propulsion system of claim 1, further comprising: an accessorygear box dedicated to the electric propulsion engine.
 5. The propulsionsystem of claim 4, wherein the accessory gear box is driven by theelectric motor.
 6. The propulsion system of claim 4, wherein thelubrication oil circulation assembly comprises a lubrication oil supplypump and a lubrication oil scavenge pump, and wherein the accessorygearbox drives the lubrication oil supply pump and the lubrication oilscavenge pump.
 7. The propulsion system of claim 4, further comprising:a sump enclosing the bearing; and a pressurization pump for pressurizingthe sump, wherein the accessory gearbox drives the pressurization pump.8. The propulsion system of claim 4, wherein the accessory gearboxincludes a secondary electrical machine.
 9. The propulsion system ofclaim 4, wherein the heat exchanger is an air cooled oil cooler.
 10. Thepropulsion system of claim 9, wherein the accessory gearbox drives ablower for providing an airflow through the air cooled oil cooler. 11.The propulsion system of claim 4, further comprising: a gas turbineengine; and an electric generator driven by the gas turbine engine, theelectric generator providing electrical power to the electric motor andthe accessory gearbox.
 12. The propulsion system of claim 4, furthercomprising: a gas turbine engine having a dedicated accessory gearbox,wherein the dedicated accessory gearbox of the gas turbine enginecomprises an electrical machine configured to generate electrical power,and wherein the accessory gearbox of the electric propulsion engine isconfigured to receive electrical power from the electrical machine ofthe accessory gearbox of the gas turbine engine.
 13. The propulsionsystem of claim 1, wherein the electric propulsion engine is configuredas a boundary layer ingestion aft fan configured to be mounted along amean line of the aircraft at the aft end of the aircraft.
 14. Thepropulsion system of claim 1, further comprising: a cooling systemoperable with an airflow over an aft end of the aircraft when theelectric propulsion engine is mounted to the aircraft, the coolingsystem configured to cool the electric motor during operation of theelectric propulsion engine.
 15. The propulsion system of claim 14,wherein the cooling system is further operable with the thermalmanagement system.
 16. The propulsion system of claim 1, wherein theheat exchanger is a thermal fluid to lubrication oil heat exchanger. 17.A boundary layer ingestion fan defining a central axis, the boundarylayer ingestion fan comprising: an electric motor; a fan rotatable aboutthe central axis of the boundary layer ingestion fan by the electricmotor; a bearing supporting rotation of the fan; and a thermalmanagement system comprising a lubrication oil circulation assembly forproviding the bearing with lubrication oil; and a heat exchangerthermally connected to the lubrication oil circulation assembly.
 18. Theboundary layer ingestion fan of claim 17, further comprising: anaccessory gear box dedicated to the boundary layer ingestion fan. 19.The boundary layer ingestion fan of claim 18, wherein the lubricationoil circulation assembly comprises a lubrication oil supply pump and alubrication oil scavenge pump, and wherein the accessory gearbox drivesthe lubrication oil supply pump and the lubrication oil scavenge pump.20. The boundary layer ingestion fan of claim 17, wherein the boundarylayer ingestion fan is configured as an aft fan configured to be mountedalong a mean line of the aircraft at the aft end of the aircraft.